graphql: fields of object should be ANDed always

[saihaj]

Let's take this query as an example

{
  musicians(where: { or: [{name: "John", id: "m2"},{bandId: "7j"}]}){
    id
  }
}

Before when the filter for OR/AND was parsed and SQL was generated it would flatten all the filters and then all the fields were ORed so it would look like

EntityFilter::Or([{name: "John"}, {id: "m2"}, {bandId: "7j"}])

After this PR it will alway AND the fields in an object and then OR the adjacent fields so it would look like

EntityFilter::Or([EntityFilter::And([{name: "John"}, {id: "m2"}]), EntityFilter::And([{bandId: "7j"}])])

[lutter]

thanks for the quick fix!